Wally West
Young, brash and impulsive, Wally West gained the power of super-speed during a freak electro-chemical accident. Now the fastest man alive, he can run at velocities approaching the speed of light. Even Superman has a hard time keeping up with him. Because of his super-fast metabolism, Wally is constantly hungry.
Also blessed with a quick wit, Wally takes a light-hearted view of saving the universe. He is the comedian of the group, a wise-cracking, easy going slacker who relies on speed, not brains, to get him out of trouble. Unfortunately, this doesn't always work, and his flippant attitude annoys his teammates who take their jobs far more seriously. Often, this over-reliance on speed will get him in over his head, and his teammates will have to catch up to rescue him. For them, there is one thing the Flash cannot do fast enough - grow up.
The Flash
Though he was one of the original seven, The Flash felt like he was always cast aside when it came to big missions; with his "big dumb mouth" (as he put it) and "immature" attitude, Wally was never seen as that serious of a hero.
When J'onn denied Mr. Miracle and Big Barda (or "Bertha" as Flash originally thought) help in rescuing their friend, Oberon, from the clutches of Granny Goodness, Flash offered his services. Though denied at first, they eventually saw his usefulness and were successful in their mission. Extracting Kalibak from the X-Pit for Granny Goodness in exchange for Oberon, Flash, Mr. Miracle and Barda boomed back to Earth to exchange Kalibak for J'onn. Posing as Kalibak, J'onn read Granny's mind, which enabled Flash to speed off to her hideout where she had Oberon tied up.
Though he went behind J'onn's back on a mission he said wasn't worth risking, J'onn had no ill feelings toward Wally; quite the opposite. Feeling some pang of regret, J'onn "hung out" with Wally for awhile, playing games.
Flash played a key role in destroying Lex Luthor / Brainiac's attempt to destroy the world. Tapping into his Speed Force, Flash tore off the Dark Heart and Brainiac layer on Lex Luthor, freeing Luthor from Brainiac's control. By doing this, however, Flash began to essentially "die"; he was transported to a Speed Forest, but before he was stuck there forever, the Justice League were able to pull him out.
After coming back, Flash remarked that if he ever went that fast again, he wasn't coming back.
